The present invention relates, in general, to syringes for introducing liquid medication into containers such as intravenous solution bags, and more particularly to an improved protective sheath, or hood, for the needle extending from the syringe body.
Syringes particularly designed for use in injecting liquid medication into containers such as flexible bags, glass bottles, or other sterile containers, wherein the medication is to be mixed with another liquid in the container, are well known. Syringes used with flexible bags, for example, are illustrated in U.S. Pat. Nos. 3,828,779 and 3,945,382, both issued to R. W. Ogle. As described in these and similar patents, such syringes comprise an elongated, generally cylindrical hollow body portion having an open end and a closed end. A boss is formed at the closed end, the boss carrying a needle which extends through the length of the tubular body portion, passing through the boss and forming an exterior cannula portion which is adapted to inject fluid into the container. A sheath is generally provided to surround the cannula portion and is mounted at one end on the boss, with the opposite end being adapted to engage the additive-receiving orifice of, for example, an intravenous (IV) solution bag. The open end of the sheath passes over the orifice and guides the cannula into and through a normally closed plug within the orifice, with the sheath generally being designed to limit the distance the cannula can travel into the orifice to prevent it from piercing the container.
Located within and concentric with the syringe housing is an inner cylindrical wall portion which is adapted to receive a vial or other container for the medication which is to be added to the IV bag. The vial includes a resilient stopper which generally has a thin central portion adapted to be pierced by the upper end of the needle carried by the syringe housing. The stopper may be provided with external threads which engage corresponding threads on the interior of the cylindrical wall portion, with the wall of the vial surrounding the wall portion and extending into the annular space between the wall portion and the syringe housing. When the vial is placed over the end of the wall portion and into the syringe, the syringe needle pierces the stopper so that the medication can flow from the vial through the needle and into the IV bag. By pressing the vial down into the syringe housing, the stopper is forced up into the vial and fluid therein is forced out through the needle.
In order to eject the fluid from the vial into the IV bag, it is often necessary to exert considerable force on the vial and syringe housing. Further, because the orifice into which the medication is injected is flexible, the relationship between the syringe and the IV bag is not constant, and it has been found that as a result the needle guide cover often breaks away from the syringe housing boss, causing breakage of the needle or, in some cases, a piercing of the IV solution bag, thereby contaminating the intravenous solution. Further, because of the relatively unsecure connection between the needle sheath and the syringe housing, the sheath can easily be broken away in handling of the syringe even before it is put into use, thus rendering the syringe useless for its intended purpose.
In the needle cover and guide structure typified by the above-mentioned patents, the outer end of the cover is constructed to provide an exact fit with a specifically shaped container orifice, thereby limiting the usefulness of the syringe to that particular container. Thus, the syringe cannot be used as a general purpose device in combination with a variety of containers without removal of the cover for the needle or cannula, and consequent exposure of the needle to contamination.